llcforweb 1 GENERAL INTRODUCTION. ..............................................................................................6 1.1 INTRODUCTION....................................................................................................................6 1.2 STRUCTURE OF THE BOOK. ..................................................................................................7 1.3 ACKNOWLEDGEMENTS. .......................................................................................................9 2 CHAPTER 2: THE EVOLUTION OF THE LEICA LENS...............................................10 2.1 PART 1:..............................................................................................................................10 2.1.1 Choice of format. ......................................................................................................10 2.1.2 Optical requirements ................................................................................................11 2.1.3 The first lens for the “Leica” format: some design aspects......................................11 2.2 PART 2: THE EXPANSION, 1930 TO 1957............................................................................13 2.2.1 The family of lenses for the Leica. ............................................................................13 2.2.2 The war period..........................................................................................................17 2.2.3 The postwar period till 1957.....................................................................................18 2.2.4 Summary for first period 1925 to 1957. ....................................................................19 2.3 PART 3: THE CHALLENGES, 1957 TO 1988 .........................................................................21 2.3.1 Evolution of the Leica camera. .................................................................................23 2.3.2 An Herculean task From 1957 to 1988 .....................................................................25 2.3.3 Evolution of the lens systems for M and R. ...............................................................26 2.3.4 The quest for image quality; .....................................................................................28 2.3.5 Containment of costs.................................................................................................30 2.3.6 Cooperation ..............................................................................................................31 2.3.7 ELC and ELW ...........................................................................................................32 2.3.8 Glass research. .........................................................................................................33 2.3.9 Design and manufacture of Leica lenses ..................................................................34 2.3.10 Summary for the second period: 1957 to 1988. ......................................................36 2.4 2.4 PART 4: THE NEW GENERATION FROM 1990 .................................................................37 2.4.1 New visions ...............................................................................................................38 2.4.2 Current status of optical design and lens manufacture.............................................41 3 CHAPTER 3: ..........................................................................................................................46 PART 1: A GENTLE INTRODUCTION TO OPTICAL DESIGN AND ABERRATIONS. ..............................46 3.1 OPTICS AND OPTICAL DESIGNERS: RAY BENDING...............................................................46 3.2 THE ORIGIN OF ABERRATIONS............................................................................................48 3.3 THE PRIMARY ABERRATIONS. ............................................................................................51 3.3.1 Spherical aberration .................................................................................................51 3.3.2 Coma Spherical aberration.......................................................................................52 3.3.3 Astigmatism...............................................................................................................53 3.3.4 Field curvature .........................................................................................................53 3.3.5 Distortion..................................................................................................................54 3.3.6 Chromatic aberrations..............................................................................................54 3.4 HIGHER ABERRATIONS......................................................................................................55 3.5 THE ANALYTICAL APPROACH IN DESIGNING LENSES..........................................................55 3.6 THE NUMERICAL APPROACH IN DESIGNING LENSES. ..........................................................56 3.7 THE DESIGNER AT WORK. ..................................................................................................57 3.8 MAX BEREK (1886 – 1949). ..............................................................................................59 3.9 ERWIN LIHOTZKY (1887 – 1941).......................................................................................59 3.10 THE CURRENT DESIGN TEAM AND DESIGN METHOD. ........................................................60 3.11 WHAT ABOUT THIS FINGERPRINT OF A LENS? ..................................................................62 4 4 CHAPTER 4: .......................................................................................................................63 PART 2: SOME ADVANCED TOPICS IN OPTICAL DESIGN AND MANUFACTURE................................63 4.1 APOCHROMATIC CORRECTION ...........................................................................................63 4.2 CAN LENSES BE CORRECTED FOR BLACK & WHITE EMULSIONS ONLY? ..............................65 4.3 ASPHERICS ........................................................................................................................65 4.4 VIGNETTING AND THE COS4-EFFECT..................................................................................68 4.5 COATING AND LENS FLARE ................................................................................................69 Page 1 of 223 llcforweb 4.6 THE USE OF FILTERS...........................................................................................................71 4.7 WIDE APERTURES AND THE GEOMETRIC FLUX. ..................................................................72 4.8 VARIO LENSES. ..................................................................................................................73 4.9 BO-KE, UNSHARPNESS AND CIRCLE OF (LEAST) CONFUSION...............................................74 5 5 CHAPTER 5: IMAGE EVALUATION.............................................................................78 5.1 INTRODUCTION ..................................................................................................................78 5.2 RESOLUTION......................................................................................................................79 5.2.1 Resolving power........................................................................................................79 5.2.2 Resolution described. ................................................................................................79 5.2.3 The shortcomings of the resolution test ....................................................................80 5.3 5.3 SPATIAL FREQUENCY AND CONTRAST ..........................................................................81 5.3.1 Spatial frequency.......................................................................................................81 5.3.2 Contrast.....................................................................................................................82 5.4 THE MODULATION TRANSFER FUNCTION..........................................................................84 5.4.1 The generation of MTF graphs. ................................................................................85 5.4.2 The interpretation of MTF graphs ............................................................................86 5.4.3 Trade off between contrast and resolution?..............................................................86 5.4.4 Are 40lp/mm enough .................................................................................................87 5.4.5 The limitations of the MTF analysis..........................................................................88 6 6 CHAPTER 4: LEICA LENS REPORTS...........................................................................90 6.1 STATE OF THE ART DESIGNS...............................................................................................90 6.2 THE QUESTION OF FOCAL LENGTH .....................................................................................91 6.3 50MM.................................................................................................................................93 6.3.1 3.5/50,Anastigmat/Elmax,1925 , ...............................................................................94 6.3.2 3.5/50,Elmar,1925, 3.5/50,Elmar,1932 and later years............................................95 6.3.3